Homebrew PCBs

Gentlemen,
For a number of years I have been using my roll solder machine to tin my 
completed etched boards for soldering.

Part of the process involves removing the tarnish from the copper before 
applying the water based flux and passing the board through the rollers.

The tarnish remover was a Multicore solders PC2 Tarnish remover.

Disaster struck last week, the plastic bottle sprung a leak and four liters 
spread over the steel shelves and finally on to the cement.

Not a pretty sight. The shelves were stripped of paint and the cement 
surface etched away.

Apparently Multicore don't make this product in this country any more. So I 
need a replacement.

The label shows it contains Thiourea and dilute Hydrochloric acid. The 
Thiourea is 4%.

Anyone know what this Thiourea is and is there a better way to chemically 
remove the tarnish.

I will most likely have to make the mixture my self as  the brand names 
available in the USA are seldom available here.

Any comments welcomed

David

On Sun, 18 Jan 2004 08:48:36 +1000, David Hopkins <davhop@...> 
wrote:

> Gentlemen,
> For a number of years I have been using my roll solder machine to tin my
> completed etched boards for soldering.
>
> Part of the process involves removing the tarnish from the copper before
> applying the water based flux and passing the board through the rollers.
>
> The tarnish remover was a Multicore solders PC2 Tarnish remover.
>
> Disaster struck last week, the plastic bottle sprung a leak and four 
> liters
> spread over the steel shelves and finally on to the cement.
>
> Not a pretty sight. The shelves were stripped of paint and the cement
> surface etched away.
>
> Apparently Multicore don't make this product in this country any more. 
> So I
> need a replacement.
>
> The label shows it contains Thiourea and dilute Hydrochloric acid. The
> Thiourea is 4%.
>
> Anyone know what this Thiourea is and is there a better way to chemically
> remove the tarnish.
>
> I will most likely have to make the mixture my self as  the brand names
> available in the USA are seldom available here.
>
> Any comments welcomed
>
> David
>
>

I know what thiourea is, it is considered a carcinogen and used in 
electroless tinning
a lot.. (probably the reason why they don't produce it any more)

I can't help you much with your tarnish remover problem, sorry, but i would
like it very much if you could describe how your roll tinning machine 
works.

thanks

st

Several weeks ago there was a thread about using HCL 
& H2O2 as an etchant. That was a god-send for 
this newbie/lurker. I have used A.P. mostly but am 
unhappy with the cost. F.C. is so nasty that I avoid it 
if possible. The HCL/H2O2 looked perfect.

Last week, I finished my bubble tank (1 gal capacity) so 
I diluted the 30% HCL with an equal amount of D.I. 
water. Due to a brain fart, I don't remember how much 
H2O2 that I added - about 1-2oz, I think..? (Too much?) 

The solution was clear so I put in my first board and the 
etch was perfect after about 15 minutes (room temp). The 
etchant turned bright, clear green by the end of the etch.
I left the bubbler on for about 1/2 hour after the etch. No 
visible color change after the etch.

Since it worked so well for the first board, I assumed that 
I had it "made". Two days ago, I put in my second board 
(4"x6"). After 30 minutes, there was no visible removal of 
the copper, however the toner was sluffing off in the areas 
of large toner (copper flow areas). I pulled the board and 
dunked in a junk board. After 45 minutes, no etch.

Hmmmm.......

I haven't a hint of a suspicion of a clue as to what happened!
It worked so well for one board, then failed miserably
Does anyone on the list have any idea why this would fail?
Unhappily, being a beginner with this, I have no equipment 
 to chemically analyze the etchant.

cheers,
johnd


"Life isn't like a box of chocolates ... it's more like a jar of
jalapenos. What you do today might burn your butt tomorrow. "

do a search and review the material, If you had 30% HCL, you needed to add
twice that volume of water, to get a 15% mix, then a teaspoon or so h2o2 -- 
Only to get it started, once you get some copper in there it becomes cupric
chloride, and will etch on it's own. Bright green is the color of good, dark
brownish green, add another teaspoon of H202,

Putting in as much h2o2 as you did probably burnt out the mixture or
exhausted it. I'd start fresh over

JT
----- Original Message ----- 

From: <Linux_Rules@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Sunday, January 18, 2004 9:47 AM
Subject: [Homebrew_PCBs] Problems with HCL/H2O2 etchant.


>
>
> Several weeks ago there was a thread about using HCL
> & H2O2 as an etchant. That was a god-send for
> this newbie/lurker. I have used A.P. mostly but am
> unhappy with the cost. F.C. is so nasty that I avoid it
> if possible. The HCL/H2O2 looked perfect.
>
> Last week, I finished my bubble tank (1 gal capacity) so
> I diluted the 30% HCL with an equal amount of D.I.
> water. Due to a brain fart, I don't remember how much
> H2O2 that I added - about 1-2oz, I think..? (Too much?)
>
> The solution was clear so I put in my first board and the
> etch was perfect after about 15 minutes (room temp). The
> etchant turned bright, clear green by the end of the etch.
> I left the bubbler on for about 1/2 hour after the etch. No
> visible color change after the etch.
>
> Since it worked so well for the first board, I assumed that
> I had it "made". Two days ago, I put in my second board
> (4"x6"). After 30 minutes, there was no visible removal of
> the copper, however the toner was sluffing off in the areas
> of large toner (copper flow areas). I pulled the board and
> dunked in a junk board. After 45 minutes, no etch.
>
> Hmmmm.......
>
> I haven't a hint of a suspicion of a clue as to what happened!
> It worked so well for one board, then failed miserably
> Does anyone on the list have any idea why this would fail?
> Unhappily, being a beginner with this, I have no equipment
>  to chemically analyze the etchant.
>
> cheers,
> johnd
>
>
> "Life isn't like a box of chocolates ... it's more like a jar of
> jalapenos. What you do today might burn your butt tomorrow. "
>
> Be sure to visit the group home and check for new Bookmarks and files:
> http://groups.yahoo.com/group/Homebrew_PCBs
>
> Yahoo! Groups Links
>
> To visit your group on the web, go to:
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>
> To unsubscribe from this group, send an email to:
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>
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>  http://docs.yahoo.com/info/terms/
>
>

----- Original Message ----- 

From: <Linux_Rules@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Sunday, January 18, 2004 2:47 PM
Subject: [Homebrew_PCBs] Problems with HCL/H2O2 etchant.


>
>
> Several weeks ago there was a thread about using HCL
> & H2O2 as an etchant. That was a god-send for
> this newbie/lurker. I have used A.P. mostly but am
> unhappy with the cost. F.C. is so nasty that I avoid it
> if possible. The HCL/H2O2 looked perfect.
>
> Last week, I finished my bubble tank (1 gal capacity) so
> I diluted the 30% HCL with an equal amount of D.I.
> water. Due to a brain fart, I don't remember how much
> H2O2 that I added - about 1-2oz, I think..? (Too much?)
>
> The solution was clear so I put in my first board and the
> etch was perfect after about 15 minutes (room temp). The
> etchant turned bright, clear green by the end of the etch.
> I left the bubbler on for about 1/2 hour after the etch. No
> visible color change after the etch.
>
> Since it worked so well for the first board, I assumed that
> I had it "made". Two days ago, I put in my second board
> (4"x6"). After 30 minutes, there was no visible removal of
> the copper, however the toner was sluffing off in the areas
> of large toner (copper flow areas). I pulled the board and
> dunked in a junk board. After 45 minutes, no etch.
>
> Hmmmm.......
>
> I haven't a hint of a suspicion of a clue as to what happened!
> It worked so well for one board, then failed miserably
> Does anyone on the list have any idea why this would fail?
> Unhappily, being a beginner with this, I have no equipment
>  to chemically analyze the etchant.

It only works when it is fresh. You'll have to add H2O2 to get it going
again, until the acid gets too dilute.

Leon
--
Leon Heller, G1HSM
Email: aqzf13@...
My low-cost Philips LPC210x ARM development system:
http://www.geocities.com/leon_heller/lpc2104.html